广播电视英语短句 第 283 课：修剪植株-3

But the flow from the stem tip prevents them from doing this. 但是，来自主干顶端的（激素）流会阻止它们这么做。

The researchers wanted to find out how this blocking happens. 研究员们希望能够发现这种阻碍（机制）是怎么发生的。

Professor Prusinkiewicz is on sabbatical leave in Australia, but he sent us an e-mail suggesting a simple way to understand the process. Prusinkiewicz教授正在澳大利亚休假，不过他给我们发来一个封电子邮件引导我们用一个简单的方式来理解这一过程。

Think of a major road crowded with traffic. 设想一个主干道上塞满了车辆。

So many cars are on the main road that the cars on the side roads cannot enter. 如此多的车占据了主干道以至于辅道上的车辆没法进入（主干道）了。